The purpose was to develop a method to analyze nuclear weapon fallout codes and apply the method to one code as an example. Codes may be evaluated by three methods: (1) comparison of code prediction with data from an actual burst, (2) comparison with an accepted benchmark code, (3) analysis of the degree of approximation of physical laws used in the code was used in this study. Some of the attributes upon which evaluation should be based are: initial cloud model, local fallout activity, activity distribution in cloud particles, source normalization constant k, and the arrival rate of activity onmore » the ground g(t). Of these attributes, many cannot be obtained directly from code output, they must be determined from an analysis of the source code or by consulting the code's author. This thesis discusses the code attributes that must be evaluated, and describes methods for evaluation based on code output. Finally, the analysis techniques are applied to the Defense Nuclear Agency Fallout Assessment System (FAS). It was found that the physics approximations used by FAS are generally good. However the code has a tendency to over-predict the dose rate close to the detonation point by as much as a factor of 25.« less

This paper outlines several improvements to the Particle Activity Module of the Defense Land Fallout Interpretive Code (DELFIC). The modeling of each phase of the fallout process is discussed within DELFIC to demonstrate the capabilities and limitations with the code for modeling and simulation. Expansion of the DELFIC isotopic library to include actinides and light elements is shown. Several key features of the new library are demonstrated, including compliance with ENDF/B-VII standards, augmentation of hardwired activated soil and actinide decay calculations with exact Bateman calculations, and full physical and chemical fractionation of all material inventories. Improvements to the radionuclide sourcemore » term are demonstrated, including the ability to specify heterogeneous fission types and the ability to import source terms from irradiation calculations using the Oak Ridge Isotope Generation (ORIGEN) code. Additionally, the dose, kerma, and effective dose conversion factors are revised. Finally, the application of DELFIC for consequence management planning and forensic analysis is presented. For consequence management, DELFIC is shown to provide disaster recovery teams with simulations of real-time events, including the location, composition, time of arrival, activity rates, and dose rates of fallout, accounting for site-specific atmospheric effects. The results from DELFIC are also demonstrated for use by nuclear forensics teams to plan collection routes (including the determination of optimal collection locations), estimate dose rates to collectors, and anticipate the composition of material at collection sites. These capabilities give mission planners the ability to maximize their effectiveness in the field while minimizing risk to their collectors.« less

The purpose of the ASME/DOE Gen IV Task 7 Part I is to review the current experience on various high temperature reactor intermediate heat exchanger (IHX) concepts. There are several different IHX concepts that could be envisioned for HTR/VHTR applications in a range of temperature from 850C to 950C. The concepts that will be primarily discussed herein are: (1) Tubular Helical Coil Heat Exchanger (THCHE); (2) Plate-Stamped Heat Exchanger (PSHE); (3) Plate-Fin Heat Exchanger (PFHE); and (4) Plate-Machined Heat Exchanger (PMHE). The primary coolant of the NGNP is potentially subject to radioactive contamination by the core as well as contaminationmore » from the secondary loop fluid. To isolate the radioactivity to minimize radiation doses to personnel, and protect the primary circuit from contamination, intermediate heat exchangers (IHXs) have been proposed as a means for separating the primary circuit of the NGNP (Next Generation Nuclear Plant) or other process heat application from the remainder of the plant. This task will first review the different concepts of IHX that could be envisioned for HTR/VHTR applications in a range of temperature from 850 to 950 C. This will cover shell-and-tube and compact designs (including the platefin concept). The review will then discuss the maturity of the concepts in terms of design, fabricability and component testing (or feedback from experience when applicable). Particular attention will be paid to the feasibility of developing the IHX concepts for the NGNP with operation expected in 2018-2021. This report will also discuss material candidates for IHX applications and will discuss specific issues that will have to be addressed in the context of the HTR design (thermal aging, corrosion, creep, creep-fatigue, etc). Particular attention will be paid to specific issues associated with operation at the upper end of the creep regime.« less